Lifting machines and, in particular, cranes typically have lifting capacity limits under which they may operate safely. These capacities generally depend on the position at which a load is maintained under a given configuration (i.e., counterweight, outrigger position, boom extension mode, etc.). Regulations generally require that a crane manufacturer provide certain tables which list the capacity of a given crane under a given configuration at various lifting positions. Those tables are sometimes referred as capacity charts. The information in such tables may be programmed in an electronic rated capacity limiter (RCL) device associated with the crane.
In preparation for a given working project, it is often necessary to determine a working range and the lifting capacity of the lifting machine made available to complete the project. Generally, the user must consult one or more work range diagrams, such as that shown in FIG. 1, in order to confirm that a given crane may operate under the range of motion necessary to complete the project. These work range diagrams, however, do not generally include any information regarding the crane's lifting capacity at a given lifting position. Therefore, the user must also consult one or more capacity tables, such as that illustrated in FIG. 2. These capacity tables generally provide a list of rated lifting capacities at various positions for a given crane under a given configuration. In the example capacity table of FIG. 2, capacities are listed for a given crane with a counterbalance load of 14,000 lb. and outriggers positioned at an intermediate position. Should the user choose to vary the configuration of the crane (i.e. change the outrigger position or modify the counterbalance load), it would become necessary to consult one or more other capacity tables.
The above procedures may be tedious and time consuming for the user. Additionally, the current tables and diagrams only provide discrete points corresponding to a given position and crane configuration at which to determine lifting capacity. Furthermore, the current procedures do not provide an efficient manner of comparing capacities across different product lines and/or crane models.
The disclosed inventions aim to address these and other shortcomings of the above procedures and to provide an improved manner of determining or evaluating lifting capacities, as outlined herein.